Magnetic winding wire, also referred to as magnet wire, is used in a multitude of devices that require the development of electrical and/or magnetic fields to perform electromechanical work. Examples of such devices include electric motors, generators, transformers, actuator coils, etc. Typically, magnet wire is constructed by applying electrical insulation to a metallic conductor, such as a copper, aluminum, or alloy conductor. The electrical insulation is typically formed as a coating that provides for electrical integrity and prevents shorts in the magnet wire. Conventional insulations include polymeric enamel films, extruded thermoplastic layers, polymeric tapes, and certain combinations thereof.
The insulation system of a magnet wire can be damaged by a wide variety of different types of events during manufacture, transport, and/or subsequent processing. As wire size increases, wires may increase in stiffness and be more susceptible to damage during manufacture and/or processing. Even minor damage to the insulation, such as a pinhole in one or more insulation layers, may result in a fault site that reduces electrical performance. Partial discharge can occur at a localized fault site and typically begins within voids, cracks, or inclusions within a solid dielectric; however, it can also occur along surfaces of an insulation material. Once begun, partial discharge progressively deteriorates insulation and ultimately leads to electrical breakdown.
In certain applications, magnet wire may be cut into sections, and each section may be worked or formed into a desirable shape for insertion into an assembly, such as an electric motor, starter-generator, etc. For example, sections of magnet wire may be formed into hairpins that are incorporated into a motor assembly. When cut, the underlying conductor is exposed, thereby subjecting the wire to an increased risk of fault sites developing. Shaping, twisting, and/or other manipulation of the wire may also result in the generation of fault sites. The risk of fault site formation may be increased with larger sizes of magnet wire. Accordingly, there is an opportunity for improved winding wires or magnet wires incorporating conformal coatings that provide additional dielectric protection for imperfections, fault sites, and/or exposed conductor portions.
Further, recent developments in certain applications have led to a demand for magnet wire designs with improved electrical properties, such as increased dielectric strength and/or increased partial discharge inception voltage (“PDIV”). The dielectric strength of a material generally refers to the maximum applied electric field that the material can withstand without breaking down. The PDIV generally refers to the voltage at which electrical discharges that do not completely bridge the insulation between electrodes or conductors start to occur. There is also an increased demand for magnet wire to function in higher temperature applications and/or environments. For certain applications, such as vehicle applications, it may also be desirable for magnet wire to be resistant to hydrocarbon oil, other chemicals, and/or moisture. For example, in some motor applications, magnet wire is at least partially submerged in transmission fluid. This transmission fluid can break down traditional magnet wire insulation materials, such as enamel insulations.
Additionally, in many applications, it is desirable to limit or minimize overall insulation thickness in order to permit a higher amount of magnet wire to be packed or formed into an electrical device coil or formed into a greater number of components for incorporation into an assembly. The performance of an electrical device is strongly correlated to an amount of magnet wire that can be placed into an available core slot area. Reducing the thickness of magnet wire insulation may permit higher power output and/or increased performance. Accordingly, there is an opportunity for improved magnet wire having desired electrical properties with limited increases or even decreases to overall insulation thickness.